Process of and device for producing blown film

ABSTRACT

A process for the manufacture of a thermoplastic blown film is disclosed. The process includes the step of extruding a blown film tube of a thermoplastic material. The outside surface of the film tube is treated with a cooling gas to solidify the film tube. This cooling gas is directed to the tube from an annular ring around the tube and the cooling gas is directed at the tube in a flow direction parallel to a wall of the film tube. The cooling gas is drawn off the tube by means of a suction ring positioned around the tube prior to flattening the tube to form a film.

The invention relates to a process of and a device for sucking offcooling gas for a film tube during the production of blown film, whereinthe film tube, after having left the annular nozzle of a blowing head,is substantially annularly blasted with cooling gas from the outsideeither radially or in parallel with the wall. The cooling gas used isnormally cooling air. However, for certain applications, it is possibleto use inert gas. The cooling gas can emerge from a cooling gas ring inseveral planes and in different quantities, and it is possible tocombine a fixed cooling gas flow and a controllable cooling. gas flow. Aprocess of and a device for said type are described in the applicant'sDE 100 29 175 A1 for example.

From U.S. Pat. No. 6,273,699 B1 there is known a device for conditioninga film tube during the production of blown film, which device comprisesa plurality of closed annular sections along the film tube; the sectionseach comprise a ring of air ejection nozzles extending parallel to thelongitudinal direction of the film tube, and at a distance therefromthey comprise a ring of air suction nozzles directed in the oppositedirection, with the former extending in the direction of production andthe latter in the direction opposed to the direction of production ofthe film tube.

DE 44 05 463 proposes a process and device for cooling a film tubeextruded from a film blowing head, wherein cooling air is blown out of acooling ring with an annular exit gap, which cooling ring encloses thetube and wherein cooling air is sucked out of a screened spacesurrounding the tube, at a distance from the cooling ring in thedirection of production of the tube at an annular aperture.

During the production or extrusion of blown film, a thermoplasticmaterial is pressed via an extruder into a blowing head out of whoseannular nozzle or annular channel there emerges a film tube which isdrawn upwards. The hot film tube is subjected to an internal excesspressure and immediately after having left the annular nozzle, it issubstantially annularly blasted with cooling gas from the outside andoptionally also from the inside, and thus cooled. From the moment ofleaving the annular nozzle, after a film tube expansion phase, thethermoplastic material substantially solidifies, whereafter the filmtube substantially retains its diameter. The place of solidification isreferred to as the “freezing limit”. After the film tube has solidified,it is guided in the longitudinal direction via a calibrating basket anda flattening device and squeezed and pulled off in the form of a flattube by an extraction device. The calibrating basket is positioned abovethe freezing limit. The diameter of the film tube and thus thesubsequent film width is variable and is varied by the internal excesspressure in the film tube and via the setting of the adjustablecalibrating basket.

During the production of blown film tube, after the hot tube materialhas left the annular nozzle, in the region of extraction of the filmtube as far as the freezing limit, monomer-containing gases emerge fromthe thermoplastic material. Said gas emissions are carried along by thepassing cooling gas in the direction of production and are deposited inthe form of a wax-like coating on all plant elements following theblowing head in the direction of extraction such as the calibratingbasket, the flattening device and the extraction tool as well on devicesin the direct vicinity. Floating particles in the environment formadditional dirt deposits on the sticky wax-like coating. Such wax anddirt deposits obstruct the production process of the film tube andadversely affect accurate functioning of the plant elements and thus theproduct quality. Particularly in the case of medical film and film forthe food industry, the transfer of dirt deposits to the film tube leadsto unacceptable quality defects. Therefore, it has so far been necessaryfor said plant elements to be cleaned regularly and extensively, whereinas a rule, access to said plant elements was complicated. Furthermore,it is suspected that breathing-in cooling gas contaminated with gasemissions in the gaseous phase is detrimental to a person's health.

It is therefore the object of the present invention to provide a processand device of said type by means of which contamination of the plantelements by exhaust gas deposits can be reduced or avoided. Theobjective is achieved by a process of said type which is characterisedin that the cooling gas contaminated with gas emissions out of the tubematerial is substantially annularly sucked off again on the outside ofthe film tube in the direction of extraction of the film tube downstreamfrom the cooling gas supply, and by a device wherein at a distance fromthe cooling gas ring, above same (downstream), there is arranged a gassuction ring which encloses the film tube and comprises internal,substantially annularly arranged suction nozzles. Such means make itpossible to suck off the cooling gas contaminated with gas emissionsnear their origin, thus avoiding or reducing the contamination of thesubsequent plant components and reducing the health risk.

According to a first embodiment of the invention it is proposed that,downstream from the freezing limit, but already upstream from acalibrating phase, the contaminated cooling gas is sucked off. The gassucking-off ring is arranged between the freezing limit and thecalibrating device, without obstructing the film tube cooling operationup to the point of reaching the freezing limit. This is particularlyadvantageous with a view to protecting the calibrating device and thesubsequent plant components from contamination.

According to a second embodiment it is proposed that the contaminatedcooling gas is sucked off in the region of the calibrating phase of thefilm tube, i.e. that the gas sucking-off ring or several gas sucking-offbeams are arranged in the region of the calibrating device for the filmtube. This means that even in the region of the open structure of acalibrating basket, contaminated cooling gas can be sucked off in such away that the components of the adjusting devices of the calibratingdevice can also be protected from contamination.

According to a third embodiment, it is proposed that the contaminatedcooling gas is sucked off downstream from a calibrating phase of thefilm tube. This means that the gas sucking-off ring is arranged above(downstream from) a calibrating device for the film tube.

According to a preferred embodiment it is proposed that the film tube issealed annularly directly downstream from the suction point relative tothe suction means. The respective device comprises a diaphragm which isarranged directly above (downstream from) the gas sucking-off ring andwhich annularly seals the film tube relative to the gas sucking-offring. On the one hand, this measure improves the effectiveness of thesuction process and, on the other hand, it fully protects the subsequentplant components such as the flattening device, from being contaminated.The diaphragm can be provided in the form of an adjustable irisdiaphragm.

More particularly, it is proposed that the iris diaphragm is providedwith automatic control means for adapting the diaphragm diameter to thediameter of the film tube. The diameter of the film tube can becontinuously recorded by contact-free ultrasound measurements. It isthus possible to compensate for slight diameter fluctuations of the filmtube in the course of production and to avoid manual adaptation measuresduring production changes.

More particularly, it is proposed that the plurality of suction beamsare connected to a segmented, adjustable calibrating device.

In a simple embodiment of the process, the sucked-off contaminatedcooling gas can be blown into the environment outside the productionhall. However, in view of environmental protection measures it ispreferred to filter the cooling gas contaminated with gas emissionsbefore it is blown out either inside or outside the production hall. Forthis purpose, more particularly, there is provided an electric filter ina suction line in front of the suction fan.

If the film tube production facilities include additional internalcooling, the contaminated, sucked-off cooling gas from the inner coolingoperation can be combined with the contaminated cooling gas of the outercooling operation and filtered together therewith.

According to a further process improvement, it is proposed that,downstream from the suction point of the contaminated cooling gas, thefilm tube, for being cooled subsequently, is again blasted in asubstantially annular way with cooling gas, i.e. that directly above(downstream from) the gas sucking-off ring, there is arranged a furthercooling gas ring. In this context, it is proposed that the renewedoperation of blasting the film tube with cooling gas takes placedownstream from the annular sealing region in that the further coolinggas ring is arranged directly above (downstream from) the diaphragm.Such means allow subsequent cooling of the still relatively warm filmtube, such subsequent cooling allowing continued interference-freehandling of the film tube, more particularly flattening same and windingsame up on a coil.

As the already heated cooling air flowing along the film tube is suckedoff completely from the film tube at the suction ring, the additionallyblasted cooling gas reaches the film tube without any obstructions froma flow-technological point of view and has a high subsequent coolingeffect because it is not mixed with the heated cooling gas. This ensuresa high production output in high-performance production facilities andthose with a low building height.

The quantity of sucked-off contaminated cooling gas can be automaticallyadapted to the quantity of cooling gas freshly supplied directly afterthe film tube emerges from the annular nozzle. For this purpose, it isnecessary to provide a suitable control device.

The inventive devices are particularly advantageous in that they caneasily be adapted to different film tube diameters, more particularly inthe region where the suction ring mentioned first is sealed relative tofilm tube by means of an adjustable diaphragm and in the region of thecalibrating device by combining individual suction beams or suctionfunnels with the segments of an adjustable calibrating device.

According to a further advantageous embodiment, it is possible tostructurally connect the suction ring mentioned first, the diaphragm andthe additional cooling ring in such a way that the assembly requiresonly one single common suspension facility in the plant frame.

Preferred embodiments of the invention are illustrated in the drawingsand will be described below.

FIG. 1 shows a film blowing plant in accordance with the invention in afirst embodiment illustrating the entire system.

FIG. 2 shows parts of the plant according to FIG. 1 in an enlargedillustration.

FIG. 3 shows a film blowing plant in accordance with the invention in asecond embodiment illustrating the entire system.

FIG. 4 shows parts of the plant according to FIG. 3 in an enlargedillustration.

In a side view and partially in a longitudinal section through the axisof a blown film tube, FIG. 1 shows a plant for carrying out theinventive process, including the characteristics in accordance with theinvention. On a machine foundation 11, there is erected an extruder 12comprising two charging hoppers 13, 14 for thermoplastic material.Thermoplastic material introduced in granular form through the hoppers13, 14 is plasticized and homogenised by the pressure means andadditional heating means in a worm of the extruder 12 and pressed into ablowing head 15 with a vertical axis, which follows the extruder. At itsupper end, the blowing head 15 comprises an annular nozzle (notidentifiable in detail) from which there emerges a expandingaxis-symmetrical film tube 16 initially consisting of a stillplasticized film material. After the material has solidified, the filmtube 16′ substantially retains its diameter. The film tube 16′ isflattened in a flattening device 17 and extracted upwards by anextraction device 18. Subsequently, the flattened film tube 16″ is woundup on coils. In the direction from the blowing head 15 to the extractiondevice 18, the functional terms “upstream from” and “downstream from”are used to mean in a spatial relationship “underneath” and “above”.

Directly above the blowing head 15, there is shown a cooling gas ring 19with several gas supply lines 20. The cooling gas ring 19 comprisesinternal exit nozzles 21 out of which there flows the cooling gas and,substantially annularly and parallel to the wall, flows against the filmtube 16 which is subjected to an increased internal pressure. Thecooling gas flow is symbolised by arrows 22. Under said internal excesspressure, the diameter of the film tube 16 plasticized in this region,until the film tube 16 hardens under the effect of the cooling gas andassumes a constant diameter. The place of transition from theplasticized material to the hardened material is referred to as the“freezing limit” and has been given the reference number 23. Above, i.e.in the direction of extraction downstream from the freezing limit 23,there is arranged a calibrating device 24 which contains rollerassemblies which are positioned one above the other and which arepositioned substantially annularly around the film tube 16′. To permitadaptation to film tubes with different diameters, the rollerassemblies, as a rule, are located on individual pivotable segmentsforming circumference parts, by means of which segments the diameter ofthe calibrating device can be changed. In a cross-sectional view, saidsegments, in a simplified way, can form a polygonal calibrating device.The still relatively warm film tube 16′ is stabilised in itscross-section by the calibrating device.

Downstream from the calibrating device 24, there is provided aninventive gas sucking-off ring 25 with internal annular suctionapertures 26, which ring 25 can suck off the cooling gas contaminatedwith gas emissions from the film tube. Circumferentially distributedsuction lines 27 are connected to the gas sucking-off ring 25. Thecooling gas contaminated with gas emissions is indicated by arrows 28.Directly downstream from the gas sucking-off ring 25, there is providedan adjustable diaphragm 29 which is mechanically connected to said ring25 and which sealingly encloses the film tube 16′. The diaphragm 29 isadjustable by an adjusting device 30 in the aperture cross-section andcan therefore be adapted to different diameters of the film tube 16′. Bysealing the film tube above the gas sucking-off ring 25, pure air isprevented from being sucked in from a region downstream from the gassucking-off ring, so that the process of sucking off the contaminatedcooling gas is optimised while keeping the energy consumption low. Inthe region of the calibrating device 24, radially outside thecalibrating device, there is provided a further gas sucking-off ring ora plurality of individual gas sucking-off funnels or gas sucking-offbeams 31 which are connected to a plurality of circumferentiallydistributed suction lines 33. One gas sucking-off beam each can beassociated with one of the above-mentioned segments, so that anadaptation of the calibrating device to different diameters of the filmtube 16′ can be accompanied by an adaptation of the additional suctiondevice to the different diameters. The plurality of suction lines 27 isfirst joined to form a line 27′. Equally, the plurality of suction lines33 is then combined to form. one single line 33′. The lines 27′ and 33′are then combined to form one single gas sucking-off line 43, with thecontrol flap 34 being arranged in the region of a Y-pipe. The suctionpipe 43 is followed by a suction fan 44. In the suction line 43, infront of the suction fan 44, there can be integrated a filter, moreparticularly an electric filter, if, for environmental reasons, it isimpossible to blow the gas emissions into the environment outside aproduction hall. A control device 36 with a processor controls via acontrol line 37 the suction fan 44 and, via a control line 38, a furthercontrol device 39 for controlling the adjusting device 30 for thediaphragm 29. Via a measuring line 40, the signals of a cooling gasquantity sensor 41 are transmitted in the cooling air supply lines 20 tothe control device 36. Via the measuring line 42, the signals on thepressure and flow quantity conditions at the electric filter 45 aretransmitted to the control device 36. Via a further control line (notillustrated), the control device 36 can regulate the cooling gas fan(not illustrated either) in a processor-controlled way. The entireregion from the first cooling gas ring 10 to the gas sucking-off ring 25is enclosed by a casing 53, so that the cooling gas contaminated withgas emissions is kept clear of the working area of the operatives. Thelines 27, 33 are sealed by the casing.

In FIG. 2, the details identical to those shown in FIG. 1 have beengiven the same reference numbers. To that extent, reference is made tothe preceding description. In this Figure it is indicated that thecooling gas ring 19 comprises two exit nozzles 21′, 21″. It can also beseen that in the suction ring 25, there are provided labyrinth elements25′ in order to level out the pressure level at the suction aperture 26across the circumference and to suppress the influence of the individualgas sucking-off lines 27. It can also be seen that in the gassucking-off beams 31 there are provided facilities 31′ in order to calmthe pressure level in the gas inlet aperture 32.

In FIG. 3, the details identical to those shown in FIG. 1 have beengiven the same reference numbers and have the same function as describedabove. In addition to the details described in FIG. 1, there can beidentified a further cooling gas ring 46 which, via inner exit nozzles47, blows cooling gas for subsequent cooling purposes substantiallyradially against the film tube 16′. The additional cooling gas streamsare indicated by arrows 48. Gas supply lines 49 which, in total, aresupplied via a supply line 50 by a further cooling gas pressure fan 51are connected to an additional cooling gas ring 46. The cooling gaspressure fan 51 is controlled via a control line 52 by the controldevice 36. The still relatively warm film tube 16′ can thus bere-cooled, so that the flattening assembly 17 and the extraction device18 can be made to operate without the risk of the film layers stickingduring the flattening operation. In this embodiment, too, the regionfrom the first cooling gas ring 19 to the gas sucking-off ring 25 isenclosed by a casing 33, which sealingly adjoins said parts and whichprevents the working environment from being subjected to cooling gascontaminated with gas emissions.

In FIG. 4, the details identical to those shown in FIG. 3 have beengiven the same reference numbers. To that extent, reference is made tothe above description. It is indicated that the cooling gas ring 19comprises two exit nozzles 21′, 21″. Furthermore, it can be identifiedthat labyrinth elements 25′ are provided in the suction ring 25 in orderto unify the pressure level at the suction aperture 26 around thecircumference and to suppress the influence of the individual gassucking-off lines 27. It can also be seen that in the gas sucking-offbeams there are provided elements 31′ in order to calm the pressurelevel in the gas inlet apertures 32. Finally, the additional cooling gasring 46 is provided with labyrinth elements 46′ to unify the additionalcooling gas stream at the exit nozzle 47. The assemblies of suction ring25, diaphragm 29 and additional cooling gas ring 46 are structurallyconnected to one another.

LIST OF REFERENCE NUMBERS

-   11 foundation-   12 extruder-   13 charging hopper-   14 charging hopper-   15 nozzle head-   16 film tube-   17 flattening device-   18 extraction device-   19 cooling gas ring-   20 cooling gas supply-   21 cooling gas ring nozzle-   22 cooling gas (arrow)-   23 freezing limit-   24 calibrating device-   25 gas sucking-off ring-   26 suction ring nozzle-   27 gas discharge-   28 exhaust gas (arrow)-   29 diaphragm-   30 adjusting device-   31 gas sucking-off beam-   32 suction slot-   33 gas discharge-   34 control flap-   35 y-pipe-   36 control device-   37 control line-   38 control line-   39 control device-   40 measuring line-   41 measuring sensor-   42 measuring line-   43 suction line-   44 suction fan-   45 electric filter-   46 cooling gas ring-   47 cooling gas nozzle-   48 cooling gas (arrow)-   49 cooling gas supply-   50 cooling gas line-   51 cooling gas fan-   52 control line-   53 casing

1-22. (canceled)
 23. A process for the manufacture of a thermoplasticblown film comprising: extruding a blown film tube (16) of athermoplastic material; treating an outside surface of said film tubewith a cooling gas to solidify said film tube, said cooling gas beingdirected to said tube from an annular ring (19) around said tube and ina flow direction parallel to a wall of said film tube; drawing off saidcooling gas from around said tube prior to flattening said tube to forma film.
 24. The process according to claim 58 wherein said suction ring(25) is downstream of a freezing limit (23) of said film tube (16). 25.The process according to claim 24 wherein cooling gas is drawn off bysaid suction ring downstream from the freezing limit (23) of the filmtube (16), but upstream from a calibrating device (24) for the film tube(16).
 26. The process according to claim 24 wherein cooling gas is drawnoff by said suction ring downstream from the freezing limit (23) of thefilm tube (16), and downstream from a calibrating device (24) for thefilm tube (16).
 27. The process according to claim 24, 25 or 26 whereina gas other than the cooling gas is not permitted to contact the outersurface of said film tube after said tube passes said suction ring andprior to flattening said film tube.
 28. The process according to claim24, 25 or 26 wherein the film tube (16) is treated with a second coolinggas downstream of said first suction ring said second cooling gas beingdirected to said tube from an annular ring (19) around said tube and ina flow direction parallel to a wall of said film tube, said secondcooling gas being drawn off by means of a second suction ring aroundsaid tube prior to flattening said tube to form a film.
 29. The methodaccording to claim 24, 25 or 26 wherein, the quantity of cooling gassuctioned off by said suction ring automatically adapts to the quantityof cooling gas supplied after the exit of the film tube.
 30. The processaccording to claim 24, 25 or 26 wherein cooling gas originating from acooling process for cooling an interior side said film tube (16) iscombined with the cooling gas from the exterior wall of said film tubeand is drawn off by said suction ring (25).
 31. The process according toclaim 24, 25 or 26 wherein said cooling gas is filtered prior toexhausting said gas to the environment.
 32. An apparatus for themanufacture of a thermoplastic blown film comprising: a blower head (15)for extruding a film tube (16) of a thermoplastic material; an annularring (19) for blowing a cooling gas on an outside surface of said filmtube to solidify said film tube, said annular ring adapted to direct thecooling gas at said tube in a flow direction parallel to a wall of saidfilm tube; and a suction means around said tube to draw off said coolinggas, said suction ring being positioned upstream of a means forflattening said tube to form a film.
 33. The apparatus according toclaim 63 wherein said suction ring (25) has a plurality of substantiallyannularly arranged suction nozzles (26).
 34. The apparatus according toclaim 33 wherein the suction ring (25) is positioned downstream of afreezing limit (23) and upstream of a calibrating device (24) for thefilm tube (16).
 35. The apparatus according to claim 33 wherein thesuction ring (25) is positioned downstream of a freezing limit (23) anddownstream of a calibrating device (24) for the film tube (16).
 36. Theapparatus according to claim 34 or 35 wherein said annular ring (19) hasan internal substantially annular cooling gas exit (21).
 37. Theapparatus according to claim 34 or 35 further comprising a suction beam(31) with internal, substantially annularly arranged suction nozzles(26).
 38. An apparatus for the manufacture of a thermoplastic blown filmcomprising: a blower head (15) for extruding a film tube (16) of athermoplastic material; an annular ring (19) for blowing a cooling gason an outside surface of said film tube to solidify said film tube, saidcooling gas being directed at said tube in a flow direction parallel toa wall of said film tube; and a suction beam (31) around said tube todraw off said cooling gas, said suction beam being positioned upstreamof a means for flattening said tube to form a film.
 39. The apparatusaccording to claim 38 wherein said suction beam (31) has internal,substantially annularly arranged suction nozzles (26).
 40. The apparatusaccording to claim 39 wherein there are a plurality of suction beamsarranged in the region of a calibrating device (24) for the film tube(16).
 41. The apparatus according to claim 32 wherein the suction ring(25) is positioned downstream of a calibrating device (24) for the filmtube (16).
 42. The apparatus according to claim 38 wherein the suctionbeam (31) is positioned downstream of a calibrating device (24) for thefilm tube (16).
 43. The apparatus according to claim 32 wherein, thereis a diaphragm (29) above the suction ring (25) which annularly sealsthe film tube (16) relative to the suction ring (25).
 44. The apparatusaccording to claim 32 wherein the diaphragm (29) is an adjustable iristhat may be adjusted to fit the diameter of the film tube.
 45. Theapparatus according to claim 38 wherein the suction beam (31) isconnected to a segmented adjustable calibrating device.
 46. Theapparatus according to claim 32 wherein directly above the suction ring(25) there is a second cooling gas ring (46).
 47. The apparatusaccording to claim 32 wherein there is a diaphragm (29) above thesuction ring (25) and a second cooling gas ring (46) above the diaphragm(29).
 48. The apparatus according to claims 32 further comprising acontrolling device (36) for controlling the amount of contaminatedcooling gas to be suctioned off,
 49. The apparatus according to claims32 wherein there is an inner film tube cooling system and a suction linefor removing cooling gas from the inner film tube is combined with asuction line for removing the cooling gas from the outer film tube. 50.The apparatus according to claims 32 wherein a filter (45) is arrangedin a gas suction line (43) in front of a suction fan (44).
 51. Theapparatus according to claims 32 further comprising a casing (53) whichseals the flow of cooling gas from the first cooling gas ring (19) tothe gas suction ring (25).
 52. The apparatus according to claim 38wherein directly above the suction ring (25) there is a second coolinggas ring (46).
 53. The apparatus according to claim 38 wherein there isa diaphragm (29) above the suction ring (25) and a second cooling gasring (46) above the diaphragm (29).
 54. The apparatus according toclaims 38 further comprising a controlling device (36) for controllingthe amount of contaminated cooling gas to be suctioned off.
 55. Theapparatus according to claims 38 wherein there is an inner film tubecooling system and a suction line for removing cooling gas from theinner film tube is combined with a suction line for removing the coolinggas from the outer film tube.
 56. The apparatus according to claims 38wherein a filter (45) is arranged in a gas suction line (43) in front ofa suction fan (44).
 57. The apparatus according to claims 38 furthercomprising a casing (53) which seals the flow of cooling gas from thefirst cooling gas ring (19) to the gas suction ring (25).
 58. Theprocess according to claim 23 wherein said cooling gas is drawn off bymeans of a suction ring.
 59. The process according to claim 23 whereinsaid cooling gas is drawn off by means of a suction beam.
 60. Theprocess according to claim 59 wherein said suction beam (31) isdownstream of a freezing limit (23) of said film tube (16).
 61. Theprocess according to claim 60 wherein cooling gas is drawn off by saidsuction beam downstream from the freezing limit (23) of the film tube(16), but upstream from a calibrating device (24) for the film tube(16).
 62. The process according to claim 60 wherein cooling gas is drawnoff by said suction beam downstream from the freezing limit (23) of thefilm tube (16), and downstream from a calibrating device (24) for thefilm tube (16).
 63. The apparatus according to claim 32 wherein thesuctions means is a suction ring.
 64. The apparatus according to claim32 wherein the suctions means is a suction beam.
 65. The apparatusaccording to claim 64 wherein said suction beam (31) has a plurality ofsubstantially annularly arranged suction nozzles (26).
 66. The apparatusaccording to claim 65 wherein the suction beam (31) is positioneddownstream of a freezing limit (23) and upstream of a calibrating device(24) for the film tube (16).
 67. The apparatus according to claim 65wherein the suction beam (31) is positioned downstream of a freezinglimit (23) and downstream of a calibrating device (24) for the film tube(16).
 68. The apparatus according to claim 33 wherein the suction ring(25) is positioned upstream of a calibrating device (24) for the filmtube (16).
 69. The apparatus according to claim 38 wherein the suctionbeam (31) is positioned upstream of a calibrating device (24) for thefilm tube (16).
 70. The apparatus according to claim 33 wherein saidsuction ring (25) has internal, substantially annularly arranged suctionnozzles (26).
 71. The apparatus according to claim 70 wherein there area plurality of suction rings arranged in the region of a calibratingdevice (24) for the film tube (16).